Author

Abstract

The effects of primary particle (particle) and cluster (aggregate) size distributions on absorption and scattering properties of simulated soot were studied both computationally and theoretically. Computational methods involved the solution of the volume integral equation formulation of Maxwell's equations using the method of moments, based on the ICP algorithm. The theoretical methods employed Rayleigh-Debye-Gans approximation for mass fractal-like aggregates (RDG-FA) formed by small particles. An extension of the RDG-FA formulation was proposed to account for polydisperse particle sizes, based on a volume correction approach. Differential and total scattering as well as absorption cross sections were considered for morphologies representative of soot found in flame environments. Aggregates were constructed using a sequential algorithm which mimics mass fractal-like structures. Log-normal and normal (Gaussian) probability density functions were employed to consider polydisperse populations of aggregates and particles, respectively. Over the range of evaluation, the effects of aggregate and particle polydispersity were negligible for the angular scattering pattern in the power-law regime. Furthermore, absorption cross section was similarly affected by polydispersity of aggregates and particles. Finally, the RDG-FA predictions generally agreed with the ICP results within 10%, confirming its applicability to predict mean optical properties of polydisperse populations of soot aggregates and particles.